1. Field of Invention
This invention relates generally to oil pumps and travelling valves used therein, and more specifically, to an improved travelling valve providing benefits in the areas of gas lock prevention, wear resistance, and efficiency.
2. Background of the Invention
In general terms, an oil well pumping system begins with an above-ground pumping unit, which creates the up and down pumping action that moves the oil (or other substance being pumped) out of the ground and into a flow line, from which the oil is taken to a storage tank or other such structure.
Below ground, a shaft is lined with piping known as xe2x80x9ctubing.xe2x80x9d Into the tubing is inserted a sucker rod, which is ultimately, indirectly, coupled at its north end to the pumping unit. The sucker rod is coupled at its south end, indirectly, to the oil pump itself, which is also located within the tubing, which is sealed at its base to the tubing. The sucker rod will couple to the oil pump at a coupling known as a 3-wing cage.
Beginning at the south end, oil pumps generally include a standing valve, which has a ball therein, the purpose of which is to regulate the passage of oil (or other substance being pumped) from downhole into the pump, allowing the pumped matter to be moved northward out of the system and into the flow line, while preventing the pumped matter from dropping back southward into the hole. Oil is permitted to pass through the standing valve and into the pump by the movement of the ball of its seat, and oil is prevented from dropping back into the hole by the seating of the ball.
North of the standing valve, coupled to the sucker rod, is a travelling valve. The purpose of the travelling valve is to regulate the passage of oil from within the pump northward in the direction of the flow line, while preventing the pumped oil from dropping back in the direction of the standing valve and hole.
Actual movement of the pumped substance through the system will now be discussed. Oil is pumped from a hole through a series of xe2x80x9cdownstrokesxe2x80x9d and xe2x80x9cupstrokesxe2x80x9d of the oil pump, which motion is imparted by the above-ground pumping unit. During the upstroke, formation pressure causes the ball in the standing valve to move upward, allowing the oil to pass through the standing valve and into the barrel of the oil pump. This oil will be held in place between the standing valve and the travelling valve. In the travelling valve, the ball is located in the seated position. It is held there by the pressure from the oil that has been previously pumped. The oil located above the travelling valve is moved northward in the direction of the 3-wing cage at the end of the oil pump.
On the downstroke, the ball in the travelling valve unseats, permitting the oil that has passed through the standing valve to pass therethrough. Also during the downstroke, the ball in the standing valve seats, preventing the pumped oil from moving back down into the hole.
The process repeats itself again and again, with oil essentially being moved in stages from the hole, to above the standing valve and in the oil pump, to above the travelling valve and out of the oil pump. As the oil pump fills, the oil passes through the 3-wing cage and into the tubing. As the tubing is filled, the oil passes into the flow line, from which the oil is taken to a storage tank or other such structure.
There are a number of problems that are regularly encountered during oil pumping operations. Oil that is pumped from the ground is generally impure, and includes water, gas, and impurities such as sand. The presence of gas in the oil can create during pumping operations a condition that is sometimes referred to as xe2x80x9cgas lock.xe2x80x9d Gas lock occurs when a quantity of gas becomes trapped between the travelling valve and standing valve balls. In this situation, hydrostatic pressure from above the travelling valve ball holds it in a seated position, while the pressure from the trapped gas will hold the standing valve ball in a seated position. With the balls unable to unseat, pumping comes to a halt.
The typical response to gas lock is to remove the oil pump and release the trapped gas. This can be time-consuming and, of course, interrupts pumping operations.
Another problem is related to the ball and seat for the ball within the travelling valve. During pumping operations, the ball is continuously being lifted off the seat, rotating, and re-seating. However, because the travelling valve ball is not coupled to the seat, it does not always perfectly center when seating. This can result in some leakage in the travelling valve and thus pumping inefficiency. Moreover, improper seating can cause damage to both the ball and the seat, which are the shortest wear items in the oil pump. When these are sufficiently worn, pumping operations must be interrupted and the entire oil pump removed for their replacement. Relatedly, while the seat can be inverted to extend its life, the constant rotation of the ball results in substantially even wear over the entire surface of the ball, making inversion to extend ball life impossible.
Still another problem is related to the impurities commonly found in the oil, such as sand. Sand can become trapped between the side of the travelling valve and the interior wall of the oil pump. When it becomes trapped in this manner, the constant up and down motion of the travelling valve can lead to scoring of the travelling valve, ultimately reducing its effectiveness and sometimes requiring its replacement. Sand can also get between the ball and seat, preventing proper seating, possibly leading to damage and inefficiency.
Yet another problem is encountered during deviated or non-vertical pumping operations. It is often necessary to conduct pumping operations in an angled or even horizontal direction, where for one reason or another, e.g., where a building is located directly over the hole, it is impossible to access the hole from directly above. In these instances, a well is sunk vertically at a distance from the site, and the well (including the oil pump) is then extended at an angle or perhaps even horizontally to the hole. Where the oil pump is operating in a non-vertical orientation, the travelling valve ball will be pulled by gravitational forces toward the side of the travelling valve, preventing it from fully seating, potentially causing damage and inefficiency.
The pumping of heavy crude also presents problems. The viscosity of this fluid can prevent the travelling valve ball from seating as quickly as it should for optimal performance. This reduces pumping efficiency.
The present invention addresses these problems encountered in prior art pumping systems and provides other, related, advantages.
It is an object of the present invention to provide an improved travelling valve that will more efficiently vent entrained gases, reducing instances of gas lock.
It is a further object of the present invention to provide an improved travelling valve with increased wear resistance for its seat and ball components.
It is a still further object of the present invention to provide an improved travelling valve which more efficiently centers the ball during seating.
It is yet a further object of the present invention to provide an improved travelling valve where the ball will experience wear from seating on only one hemisphere, permitting inversion of the ball to extend its life.
It is a further object of the present invention to provide an improved travelling valve that will more efficiently pass impurities through and around the valve, reducing damage to the outside of the valve, ball and seat.
It is a still further object of the present invention to provide an improved travelling valve that will allow the ball to properly center on the seat during deviated or non-vertical pumping operations.
It is yet a further object of the present invention to provide an improved travelling valve that will efficiently seat and unseat the ball during the pumping of highly viscous fluids such as heavy crude.
In accordance with one embodiment of the present invention, an improved travelling valve for use in a pumping apparatus is disclosed. The improved travelling valve comprises, in combination: a ball having a passage therethrough; a seal stem adapted to couple to the ball through the passage; an anchoring assembly adapted to anchor the ball to the seal stem; a seat positioned on the seal stem below the ball; and a drag plunger coupled at a first end thereof to the seal stem.
In accordance with another embodiment of the present invention, an improved travelling valve for use in a pumping apparatus is disclosed. The improved travelling valve comprises, in combination: a ball; a seat positioned below the ball; and means for imparting rotational movement to at least a portion of the improved travelling valve during pumping of fluid.
In accordance with another embodiment of the present invention, a method for pumping fluid is disclosed. The method comprises, in combination: providing a ball having a passage therethrough; providing a seal stem adapted to couple to the ball through the passage; providing an anchoring assembly adapted to anchor the ball to the seal stem; anchoring the ball to the seal stem with the anchoring assembly; positioning a seat on the seal stem below the ball; coupling a drag plunger at a first end thereof to the seal stem; and pumping fluid through the travelling valve.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.